Heres the postmortem on how it all worked out:
First, I really liked some of the DIY configurations presented in this thread but Im terribly pressed for time at the moment. So, I opted to go w/ the NH parts instead of rolling my own. Thank you very much to all who responded!
The parts you need are:
1) mounting bracket SBA355761281
My dealer doesnt stock this part and special ordered it. Oddly enough the brack is made in Japan! Dont we make anything here anymore????
2) Light w/ built in switch...made by Speaker. The label reads 900F-1/H9406-12
V AGRI-BRITE
1229985
Molded into the plastic case is PN 6342340.
Not sure which part of that the NH dealer uses as a part no. The light comes w/ a loop connector for ground, and male & female push connectors for the hot lead. Additonally the lamp is mounted on a bracket that allows horizontal and vertical movement.
How to wire it:
My tractor (TC24D) is prewired for a worklight on the left fender. First, strip and crimp the male push connect to one of the leads coming out of the work light. Strip and crimp the loop connector onto the other. The loop connector isnt big enough to let the ROPS bolt thru so I expanded it by making a cut in it then pulling the halves gently outward. Attach the mounting braket to the lamp and tighten. Undo the rear interior ROPS bolt on the left side of the tractor. Slip the bolt thru the mounting bracket, loop connector and then into the fender. Rethread the bolt/lock washer and tighten. Take the rubber guard off the prewired work light lead and push the connectors together. Youre done.
This light is nice and bright (as much as I could determine in full day light) and looks like its in a useful location. We're supposed to get snow again this w/e so Ill let you know how well it all works out if Im out after dark.